Hi, Cyril my betta is really really sick and worried its Dropsy. His scales look slightly raised but not 100% sure. He doesn't have a bloated stomach.

About a week ago he suddenly became lethargic and started lying on the tank floor. He still swam to the surface for air and ate fine (gave him frozen blood worms). He hasn't shown any sign of scratching against anything or bumping into anything. He is just still on the bottom.

Maybe 2 days ago, he started gasping for air.

Today he has stopped eating at all.

Checked his water perameters when first noticed he'd changed. Ammonia was slightly high but still less than 0.25. Nitrites and Nitrates were 0. (I use the liquid kit, not the strips).

I did a 50% water change on day one and have been doing a 20% water change daily since.

I tried treating with Wonder Tonic (as that is what brought him back last time he was sick with velvet and he made a full recovery) but hasn't worked this time.

He is just laying on the floor with his head pointed upwards gasping for air. He is still swimming to the top for air though, and will swim away quickly if I put my finger near him.

I have just put an air stone in now.

He is the only fish in a 5G tank with filter and heater set at 80degrees. I've had him for 18 months and he's always been in this tank.

Unfortunately when they start to pine cone, its usually too late. I've seen it happen before to my favourite betta who passed away a couple of months ago. Wonder Tonic will not do anything for dropsy. You could try Kanaplex by Seachem to see if that helps him, but like I said, its a slim chance. The pine coning of his scales that you're seeing means he's going into organ failure. I would lower the water level to help him, keep his temperature up, lights low, and just overall do whatever you can to make him most comfortable.

It is very visible pine coning from the pictures, yes. And I'm sorry. :( I know what it feels like to watch this happen to a fish... It really all depends on the root cause of the organ failure. Some cases can have a rebound and the fish can recover if its treated fast enough, but in some cases it can't. In my case, it was a very vicious case of septicemia that caused dropsy and caused death within 48 hours.

There are medications for raised scales and dropsy, but I haven't heard of a fish recovering.
If he's not eating, put it a food stone (Like the ones you put in when you go on vacation) so he can choose when he wants to eat.
Raising the temperature may accelerate his condition, however use your judgement.
Cleaning the water will help prevent other sicknesses from attacking his now weakened immune system, but be prepared, as he might contract other diseases.
When my brother's fish had dropsy, aside from giving him medication to treat dropsy, I gave him a salt bath, which dramatically improved his attitude.
However, it did not stop his death.
I have read of people buying very small needles, sedating their fish with clove oil, and removing the fluid that causes the swelling, then treating the wound with concentrated salt water.
This is a temporary solution, and although the fish's health improves, I have again never heard of a fish surviving for very long.

So sorry to hear that your fish is going through this, and I hope he gets through it okay.